RE: 16V Scirocco (tranny blow up)

["Snow, Jason" <SnowJ@aetna.com>]

-----Original Message-----
From: Snow, Jason 
Sent: Wednesday, September 29, 1999 1:30 PM
To: 'Scott Williams'
Subject: RE: 16V Scirocco (tranny blow up)


Scott you mad dog, you are funny as hell, and probably a better driver than
me, all I can see is it's always worked for me, and I never missed a beat
out of the turn, don't understand all that math and science stuff, but I got
a kick out of this anyway...When I am in NJ and have my car, I should drop
by and have you test drive it for me, I hear a guy can learn a lot when you
the Scott man tests drives your car....That's the rumor anyway...You crazy
lunatic you...

-----Original Message-----
From: Scott Williams [mailto:sfwilliams@home.com]
Sent: Wednesday, September 29, 1999 12:52 PM
To: scirocco list
Subject: Re: 16V Scirocco (tranny blow up)


16v Jason is absolutely right about this for every reason. There is no way
that
you can exceed the traction limitation of your tires. Let's say that the
maxium
braking force applied by friction *between the tires and the ground* (your
engine
doesn't directly stop your car unless it is dragging on the ground.) can be
expressed numerically as a value of 1. Assume also that your brakes are
powerful
enough to put the number up to say.. 1.25. What happens, the braking force
exceeds
the available traction and the car slides.

Now, let's use the engine to help slow the car. All braking force generated
by the
application of engine compression transmitted *to the tires* via the
drivetrain
comes to a number of the magic value of 1. Okay? What happens? The car slows
at
100% of it's max decelleration rate. Right. Now, downshift to a lower gear
and
increase the braking force to 1.25 again. What happens now? The car looses
traction and slides forward all over again. Consider what your theory
assumes,
that engine braking transcend the laws of physics.

See, it really is a matter of how much traction you have. Period. Engine
braking
will never increase the amount of available traction that the tires can
generate.
Stickier tires will help. A driving surface with a higher coefficient of
friction
(asphalt vs. ice) will help. Engine braking does nothing for you except for
instances where you don't have *enough* brakes to do the job..

If you can stomp on the brakes and lock them up, good! Now you know what the
braking threshold is. And it is a hell of a lot easier to modulate your
decelleration rate with the brakes than it is with the clutch.

Okay, let's directly address Mr. Snow's analysis:

> 1.) I have a someone following me into a curve, let's say I don't know,
> YOU...your right on my ass, I hit the brake, because I am going faster
than
> I should, now your even closer
>
Yes, I'm even closer for that very moment only if I've waited too long to
brake
also. Everything else equal, I'll have to slow down just like you in a
moment. And
then you've regained the same lead that you had before.

> , and let's say, my brakes lock...DOH! now we
> are both floating around with harps...
>
NOT if you *modulate* the braking force with your foot on the brake pedal.
-something that you can't do effectively with engine braking.

> OR I downshift, let the car hold itself back
>
There's nothing wrong with *downshifting*. You must do it to stay in your
powerband. However, you're forgetting the revmatching part of the equation.
The
ideal is to downshift and create a netzero effect on the decelleration rate.
SMOOTHNESS is key. It all becomes liquid when you're doing it right.

> and now at the end of the curve, I am stabbing the gas,
>
Check the vocabulary. You shouldn't be stabbing anything. I don't know
whether
that was just a matter of expression or whatever, but a very smooth
application of
power is what you want. Forgive me if that was just a semantic issue and not
a
critique of your real technique.

> AND I am in a lower gear, if you use your brake, you are
> wondering why I am 3 or four car lengths ahead of you.
>
Nope, I did my braking earlier in the turn and the used the excess traction
that I
had left over for cornering force. I then passed you on the inside of the
turn
while you were scrubbing off speed. Since I have also kept my car in the
correct
powerband I then rocket past you while you consider the math.

Yes, I'm being mildly sarcastic. Don't be offended; I'm just having a little
fun
with this.

> 2.) Downshifting [and engine braking]into a curve is better than braking.
>
No it ain't! Think about it.
--
Scott F. Williams
NJ Scirocco nut
SCCA ProRally driver
Hotrod Rabbit GTi


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